Organic light-emitting diodes (OLEDs) are thin-film light-emitting devices made of organic semiconductor materials and driven by a DC voltage. OLEDs are made with very thin organic coatings and glass substrates, and require no backlight. When a current flows through, the organic materials emit light.
In general, the brightness of the individual pixels is different due to various reasons, for example, difference in electrical characteristics of each driving transistor, variation of the high potential driving voltage at different display locations, and degradation of the OLEDs. Accordingly, the brightness of the OLED display is non-uniform. When this difference intensifies, image remnant trace appears and the image quality is deteriorated.
In order to improve the display result of an OLED display, pixel compensation is generally provided on the OLEDs. The pixel compensation methods may include internal compensation and external compensation. The internal compensation refers to a compensation method using a bootstrap circuit constructed with a thin film transistor inside a pixel. The external compensation refers to a method whereby the electrical or optical characteristics of the pixel driving circuit are sensed by an external driving circuit or a device, and then compensated. In the existing methods for compensating the OLED in the pixel driving circuit, although the compensation of the OLED is accomplished, the brightness of the OLED cannot be guaranteed to be constant, so that the display result of the organic light emitting display panel after the compensation is still less than ideal.